Switched current sources may be used as the building blocks of complementary metallic oxide semiconductor (CMOS) circuits, such as digital-to-analog (D/A) converter circuits, that use digital input signals to control the switch portion of the current source. The switch portion may be implemented using a p-channel MOS (PMOS) transistor or an n-channel MOS (NMOS) transistor.
The switch portion may be placed in the analog portion of the circuit. The digital input signals that control the switch portion are often part of a digital portion. The digital portion and the analog portion may have separate power supplies. Occasionally, the digital power supply is exposed to a higher noise ratio than the analog portion. As a result, the noise in the digital portion may be transferred to the analog portion through the digital input signal.